According to the National Health Survey, the heights of adult males in the Unite
ID: 3134358 • Letter: A
Question
According to the National Health Survey, the heights of adult males in the United States are normally distributed with mean 69.0 inches and standard deviation 2.8 inches.
(a) What is the probability that an adult male chosen at random is between 64 and 74 inches tall? (Round your answer to three decimal places.)
(b) What percentage of the adult male population is more than 6 feet tall? (Round your answer to one decimal place.)
%
Explanation / Answer
Normal Distribution
Mean ( u ) =69
Standard Deviation ( sd )=2.8
Normal Distribution = Z= X- u / sd ~ N(0,1)
a.
To find P(a < = Z < = b) = F(b) - F(a)
P(X < 64) = (64-69)/2.8
= -5/2.8 = -1.7857
= P ( Z <-1.7857) From Standard Normal Table
= 0.03707
P(X < 74) = (74-69)/2.8
= 5/2.8 = 1.7857
= P ( Z <1.7857) From Standard Normal Table
= 0.96293
P(64 < X < 74) = 0.96293-0.03707 = 0.9259
b.
P(X > 72) = (72-69)/2.8/ Sqrt ( 1 )
= 3/2.8= 1.0714
= P ( Z >1.0714) From Standard Normal Table
= 0.142
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